implantable mri compatible medical lead with a rotatable control member

ABSTRACT

A medical implantable lead is adapted to be implanted into a human or animal body for monitoring and/or controlling of an organ inside the body. The lead has in a distal end, a combined fixation means and electrode member in form of a helix, which is connected to a rotatable tubular member being connected to a rotatable member at a proximal end of the lead, and which is rotatable in relation to the lead and extendable out from the distal end, by rotation of the control member and the tubular torque transferring member, to be able to fixate the distal end of the lead to the organ by being screwed into the tissue. The helix is electrically connected to a connector at the proximal end by means of at least one electrically conducting wire formed as an electrically conducting coil, which is separate from the tubular torque transferring member and unrotatable in relation to the lead and that has one or more individual wires, each including an electrically conducting wire core and a surrounding electrically insulating layer, wherein the rotatable control member is rotatable within the connector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a medical implantable lead of the kind beingadapted to be implanted into a human or animal body for monitoringand/or controlling of an organ inside the body, comprising at a distalend a combined fixation means and electrode member in form of a helix,which is connected to a rotatable tubular torque transferring memberbeing in its turn connected to a rotatable control member at a proximalend of the lead, and which is rotatable in relation to the lead andextendable out from the distal end, by rotation of the control memberand the tubular torque transferring member, to be able to fixate thedistal end of the lead to the organ by being screwed into the tissue,wherein the helix is electrically connected to a connector at theproximal end by means of at least one electrically conducting wire.

2. Description of the Prior Art

It is well known in the art to use a medical implantable lead of theabove kind to monitor and/or control the function of an organ inside ahuman or animal body, for example to monitor and/or control a heart bymeans of a monitoring and/or controlling device in form of a pacemakeror cardiac defibrillator connected to the proximal end of the lead. Themedical implantable lead is provided with at least one electricalconductor, in form of a coil having one or more helically formedelectrically conducting wires, sometimes also referred to as filars,which connects one or more connectors arranged at the proximal end ofthe lead with one or more electrodes in its distal end. At least one ofthe electrodes is formed as a helix, which is adapted to be screwed intothe tissue of the organ for receiving and/or transmitting electricalsignals from and/or to the organ and transmit them, through theelectrically conducting coil, to the monitoring and/or controllingdevice connected to the proximal end of the lead. The helix alsofunctions as an attachment means for attaching the distal end of thelead to the organ by being rotatably extended out from the distal end ofthe lead and accordingly screwed into the tissue of the organ. Toaccomplish the rotation of the helix, it is mechanically connected tothe innermost one of the electrically conducting coils, whichaccordingly has to be rotatable in relation to the lead as well as besufficiently rigid to be able to transmit the required torque from theproximal to the distal end. The lead may also be provided with one ormore additional electrodes separate from the helix and e.g. be formed asa contact electrode, abutting against a surface of the organ, or beformed as a so called indifferent electrode which is surrounded by bodyfluids such as blood.

Normally, such medical implantable leads are not considered to becompatible with Magnetic Resonance Imaging (MRI), i.e. persons oranimals having such a lead implanted into the body, are excluded frombeing examined by MRI-scanning. This is due to the fact that theelectromagnetic field, that is generated during the MRI-scanning, willinduce a current in the conductor, which connects the one or moreelectrodes at the distal end of the medical implantable lead with themonitoring and/or controlling device at the proximal end of the lead.This induced current may cause heating at an electrode being in contactwith the tissue of the organ, especially if the electrode is in form ofa helix which is penetrated into and embedded within the tissue. If theheating is too high, there is a risk that this will cause damages to thetissue. However, the use of MRI-scanning for diagnostics is growingextensively and an increasing number of the population having a leadimplanted would benefit from MRI-scans. It is thus desirable to reduceany heating at or close to the lead tip to acceptable and safe levels toallow MRI-scanning also of persons or animals having such a leadimplanted.

It is known in the art to provide such medical implantable leads with anelectrical shielding, in form of a tube of braided wires, whichsurrounds the coil and which in its proximal end normally is connectedto the casing of the monitoring and/or controlling device. However, suchshielded medical implantable leads are associated with severaldisadvantages. On the one hand, the braided shielding will give themedical implantable lead an increased thickness as well as increasedrigidity, which normally is not desirable. On the other hand, it hasappeared that such a braided shielding cannot prevent the induction ofelectrical current to the coiled conductor in a degree that issufficient to, without risk, expose an individual, having an implantedlead, to a MRI-scanning.

U.S. Pat. No. 7,363,090 discloses a way to reduce heating caused byinduced current from MRI-scanning by connecting a contact electrode andan indifferent ring electrode in series with a band stop filter, whichare tuned to certain frequencies utilized during MRI-scanning. Such aprior art medical implantable lead comprises passive electroniccomponents, which contribute to making the lead more complex and thusmore costly to manufacture.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a medical implantable lead,which in a simple and cost-effective way reduces the induction ofcurrent from an electromagnetic field into the electrically conductingcoil.

The basis of the invention is the insight that the above object may beachieved by separating the function of effecting rotation and extendingthe helix out from the distal end of the lead, from the function oftransmitting the electrical signals between the helix and, whereappropriate, the one or more further electrodes at the distal end andthe one or more connectors at the proximal end, i.e. to split thesefunctions on separate members within the lead. More precisely, thefunction of transmitting a torque from the proximal end to the distalend for effecting rotation of and extending the helix out from thedistal end, is effected by an inner tubular torque transferring member,which has no electrically conducting function to or from the electrode,whereas the electrically conducting function to and from the electrodeis effected by a separate electrically conducting coil formed of one ormore helical wires. Each wire is moreover coated with an electricallyinsulating layer, such that the coil will form an inductor, which willallow the low frequency signals between the electrode and the monitoringand/or controlling device to pass through without being exposed to highimpedance. On the other hand, for induced current from high frequencyelectromagnetic fields, such as fields from MRI-scanning typicallyoperating at 64 or 128 MHz, the impedance in the electrically conductingcoil will be very high which to a large extent will restrain inducedhigh frequency currents.

According to the invention, also at the proximal end of the lead, thefunction of performing rotation of the torque transferring member, andconsequently the helix, is separated from the function of conducting anelectrical current between a connector at the proximal end via theelectrically conducting coil and the helix. More precisely, the rotationof the torque transferring member is effected by rotation of a controlmember at the proximal end, which control member is connected to thetorque transferring member and rotatably arranged coaxially within aconnector. The connector is in turn electrically connected to theelectrically conducting coil, which is rotatably fixed in relation tothe lead. In case the torque transferring member and/or the controlmember is electrically conductive, the connector and the control memberare electrically insulated from each other to prevent induced currentfrom a magnetic field into the torque transferring member and/or thecontrol member to be transmitted to the connector and the electricallyconducting coil, as well as the helix. In other words, the lead isarranged such that the electrical connection between the helix and theconducting wire is maintained regardless of the rotational position ofthe helix, while no electrical connection is present between the helixand the tubular torque transferring member even though the helix isrotatable by means of the tubular torque transferring member, and therotatable control member is rotatable within the connector.

By forming the medical implantable lead in this way, it is possible toform the tubular torque transferring member with a sufficient mechanicalstrength and stiffness to be able to transfer the torque required, fromthe proximal end to the distal end, to rotate the helix for extending itout from the distal end of the lead and screw it into the tissue. Theelectrically conducting coil, on the other hand, can be optimized topresent an as high inductance as possible. For example, since theelectrically conducting coil does not have to transfer any torque to thehelix, it can be formed of one or only a few wires, which each can bemade very thin. In this way, the pitch of the individual wires of thecoil will be very low, which will increase the inductance of the coil.Also, since the electrically conducting coil will be positioned aroundthe torque transferring member, the diameter of the coil can be madelarger than what is possible with the prior art combined electricallyconducting and torque transferring coils. This will also increase theinductance.

Within this overall idea, the invention may be modified in manydifferent ways. As stated, the torque transferring member is tubularhaving an inner bore. This is done for the purpose of allowing insertionof a guide wire into the inner bore to enable guiding of the distal endof the lead to a desired location inside a body. Hence, the diameter ofthe inner bore is large enough for the guide wire to be inserted intothe bore. Besides this requirement, the torque transferring member canbe formed in many different ways. In the prior art, the torquetransferring member is normally formed of three to five comparativelythick, metallic wires in order to function both as an electricalconductor as well as a torque transferring member. The several ratherthick wires will give the coil a sufficient mechanical strength totransfer the required torque, but will also give the coil a rather largepitch, which will reduce the inductance. Also, the torque transferringmember according to the invention may be formed in a similar way, withthe exception that the wires are not electrically conducting between anelectrode at the distal end and a connector at the proximal end.However, the torque transferring member could also be formed of anelectrically non-conducting material, such as e.g. a polymeric material,which can be formed as a coil of one or more helical threads or as aflexible tubing.

The medical implantable lead can be provided with more than oneelectrode, e.g. two electrodes for a bipolar lead, three electrodes fora tripolar lead, etc. The electrically conducting wires for eachelectrode can optionally be provided in separate coils, which areco-axially arranged in relation to each other, or two or more separateelectrically conducting wires, dedicated for different electrodes, canbe provided side by side in one and the same coil. One advantage with anembodiment according to the latter case is that the overall diameter ofthe lead can be made smaller than in the former case. However, theinductance will be somewhat lower in the latter case in relation to theformer, since the pitch of each individual wire will be somewhat larger.This can be alleviated by forming the coil from wires having asufficient thin cross section.

Since the helix functions as an electrode, and is rotatable in relationto the lead, together with the torque transmitting member, arrangementsshould be made in respect of the electrical connection of the helix tothe electrically conducting coil. This is due to the fact that theelectrically conducting coil dedicated for the helix is non-rotatingwhile the torque transferring member is rotatable in relation to theelectrically conducting coil. The electrical connection between thehelix and the coil can be ensured by e.g. arranging a sliding electricalcontact between the helix and the specific wire. However, the electricalconnection between the electrically conducting coil and the helix may bemaintained also in many other ways, as realized by the skilled person.

In a medical implantable lead according to the invention, the mechanicaltransfer of torque from the proximal to the distal end, for rotating andextending the helix for screwing it into the tissue, is separated fromthe electrical conducting between the monitoring and/or controllingdevice and an electrode member in form of a helix at the distal end.More precisely, the torque is transferred by means of a tubular torquetransferring member, which does not transfer any electrical currentbetween the monitoring and/or controlling device and the helix. On theother hand, the electrical signals are conducted by a coil arranged onthe outside of the torque transferring member and formed by helicallywound wires having an outer non-conducting layer, such that adjacentloops of the coil will be electrically insulated from each other and thecoil will function as an inductor. By a medical implantable lead formedin this way, it is possible to achieve a sufficient inductance in theconducting coil to prevent or at least reduce the strength of inducedhigh frequency current from an electromagnetic field, into theelectrically conducting coil to a sufficient degree that is harmless forthe tissue. At the same time, the torque transferring member can be madewith a sufficient strength and rigidity to allow transferring of thetorque required. In embodiments of the invention, the electricallyconducting coil may e.g. be formed of a wire comprising a silver core,which presents an advantageous low resistance to the signals andtherefore can be given a small cross sectional dimension, such that thecoil can be formed with a small pitch which will increase theinductance. The non-conducting layer around the wire core may be formedof a mineral or a polymer, such as e.g. ETFE (Ethylene Tetra FluorEthylene).

Since the inner tubular torque transferring member is mechanicallyconnected to the helix but has no electrically conducting function toand from the helix, whereas the electrically conducting coil arrangedoutside of the tubular torque transferring member is not adapted tomechanically transfer any torque to the helix, the one or moreconducting wires in the electrically conducting coil are arranged toalways maintain the electrical connection between a connector at theproximal end and the helix at the distal end irrespective of the rotatedposition of the tubular torque transferring member and the helix.

Within the overall idea, the invention may be altered and modified inmany different ways. For example, the tubular torque transferring membermay optionally be formed as a flexible tube or as a helical coil of oneor more threads or wires. It may also optionally be formed of anelectrically insulating or a conducting material. In the former case nospecial measures has to be taken for insulating the tubular torquetransferring member electrically from the helix or from the connector atthe proximal end, such as may have to be done in case the tubular torquetransmitting member is formed of an electrically conducting material.The connecting structure at the proximal end of the lead, which isadapted to be connected to a monitoring and/or controlling device, isformed with a connector pin which comprises an inner control member anda connector arranged co-axially outside of the control member.Accordingly, at least a part of the outer surface of the connector pinwill be formed by the connector, which is electrically connected to anelectrically conducting coil and the helix and which is adapted to beelectrically connected to the monitoring and/or controlling device. Thecontrol member is rotatably arranged within the connector andmechanically connected to the torque transferring member and the helix.The control member can optionally be entirely surrounded by theconnector such that only a proximal end of the control member is visibleand accessible, in which case some form of engagement means has to beformed at the end surface for engagement with a suitable rotary tool forperforming rotation of the torque transferring member and the helix, orproject a distance out from the proximal end of the connector such thatit forms a part of the surface of the connector pin. In the latter caserotation may be performed by gripping the control member by means of agripping tool around the outer surface. Preferably, the projecting partof the control member is formed with an enlarged cross section such thatit will have the same diameter as the connector. Moreover, the controlmember is preferably electrically insulated from the connector in casethe torque transferring member and/or the control member is electricallyconductive, e.g. metallic. The electrical insulation can preferably beformed as a sleeve surrounding the control member, but could also beformed as e.g. two ring members at a distance from each other. Thecontrol member may either be rotatable within the electrical insulation,or the electrical insulation may be rotatable within the connector.

The embodiments described and illustrated hereinafter are given solelyfor exemplifying reasons and are not intended to be comprehensive.Accordingly, many other embodiments could be conceivable within thescope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a medical implantable lead.

FIG. 2 is a view in an enlarged scale of the lead in FIG. 1 in ashortened state showing only the proximal and the distal ends of thelead.

FIG. 3 is a longitudinal section along the line A-A in FIG. 2 of aportion of a medical implantable lead according to a first embodiment.

FIG. 4 is a cross section along the line B-B in FIG. 2 of the leadaccording to FIG. 3.

FIG. 5 is a longitudinal section along the line A-A in FIG. 2 of aportion of a medical implantable lead according to a second embodiment.

FIG. 6 is a cross section along the line B-B in FIG. 2 of the leadaccording to FIG. 5.

FIG. 7 is a longitudinal section through a distal portion of the medicalimplantable lead, illustrating an embodiment of the electricallyconnection to the electrodes as well as the mechanically connection tothe helix, which is in a retracted state.

FIG. 8 is a longitudinal section according to FIG. 7 with the helix inan extended state.

FIG. 9 is a longitudinal section through the proximal end of a leadaccording to a first embodiment of the invention.

FIG. 10 is a combined longitudinal section and perspective view of thelead according to FIG. 9 together with a perspective view of a rotarytool.

FIG. 11 is a perspective view of the proximal end of the lead accordingto FIGS. 9 and 10.

FIG. 12 is a perspective view of a rotary tool for interaction with amedical implantable lead according to FIGS. 9-11.

FIG. 13 is a longitudinal section through the proximal end of a leadaccording to a second embodiment of the invention.

FIG. 14 is a combined longitudinal section and perspective view of thelead according to FIG. 13.

FIG. 15 is a perspective view of the proximal end of the lead accordingto FIGS. 13 and 14.

FIG. 16 is a perspective view of the proximal end of the lead and aclamp gripping around the control member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is first made to FIG. 1, in which is illustrated a medicalimplantable lead according to the invention in a perspective view. Thelead has a connecting structure 1 at a proximal end for connection to anot shown monitoring and/or controlling device such as a pacemaker orthe like, an intermediate flexible lead part 2, and a so called header 3at a distal end. The header is provided with a helix 4, which can bescrewed out in the axial direction of the lead from a cavity at thedistal end of the header. The helix has the function of attaching thedistal end of the lead to the heart, by being screwed into the tissue,and also functions as an electrode for receiving and/or transmittingelectrical signals from and to the tissue, respectively. The header isalso provided with a second electrode, a so called indifferent electrode5, which is formed as a ring and positioned a small distance from thedistal end and has the purpose of forming a complete current pathtogether with the helix.

The proximal and the distal ends of the lead according to FIG. 1, areillustrated in an enlarged scale in the shortened representation of thelead in FIG. 2. The helix 4 for fixation of the distal end of the leadto tissue as well as for function as an electrode is shown in anextended state. However, during insertion of the lead into a body, thehelix is retracted into the bore of the header 3 having a tubular shapeat the distal end. In addition to a tip electrode in form of the helix,which is adapted to be screwed into the tissue, the lead has, as ismentioned above, a second electrode in form of the ring electrode 5 on ashort distance from the distal end.

At the proximal end, the connecting structure 1 for connection to a notshown monitoring and/or controlling device comprises a first fluid tightsealing member 6 and a second fluid tight sealing member 6′. The sealingmembers are formed of an elastic material, in order to achieve a fluidtight connection to a socket recess of the monitoring and/or controllingdevice. In the area being positioned proximal in relation to the firstsealing member 6, the lead is provided with a first electricallyconducting connector 7 and in the area between the first and secondsealing members the lead is provided with a second electricallyconducting connector 7′, as is described more in detail below, which areadapted to be electrically coupled to mating connectors inside themonitoring and/or controlling device. The first connector 7 is inelectrical contact with the helix 4, whereas the second connector 7′ isin electrical contact with the ring electrode 5 by means of one or moreelectrical conducting coils inside the lead, as is to be explained morein detail below. In the most proximal end, the lead is provided with arotatable control member 8, which in the embodiment of FIG. 2 issurrounded by the first connector 7 and accordingly not visible therein.The control member 8 is, according to the invention, separated from theconnectors 7, 7′ and by means of the control member the helix 4 can berotated and screwed out from the bore inside the header 3 and into thetissue.

Now reference is made to FIGS. 3 and 4, in which are illustrated a firstembodiment of the flexible lead part 2 in a longitudinal section as wellas a cross section through the lead, respectively. The lead comprises aninner tubular torque transferring member 9, an inner fluid tight tubing10, an electrically conducting coil 11 and an outer fluid tight tubing12. The inner tubular torque transferring member is rotatable arrangedinside the inner tubing and is formed as a coil of five comparativelythick and rigid helical wires of e.g. metal or polymer, such that it iswell suited for transferring of a torque from the proximal to the distalend of the lead. Moreover, the torque transferring member 9 defines aninner bore 13 for the purpose of allowing insertion of a guide wire orthe like for guiding the tip of the lead to a desired position inside abody. The electrically conducting coil 11 is composed of two separate,co-radially wound wires 14, 14′, each having an electrically conductingcore 15 and a surrounding electrically insulating layer 16, such thatthey form two electrically separated inductance coils.

With reference also to FIG. 2, it is to be understood that the structureof the flexible lead part 2 as illustrated in FIGS. 3 and 4, extendsfrom the connecting structure 1 at the proximal end to the header 3 atthe distal end. Moreover, the tubular torque transferring member 9 is inits proximal end mechanically connected to the rotatable control member8 and in its distal end mechanically connected to the helix 4, such thatby rotating the rotatable control member it is possible to rotate thehelix and extend it out from the inner bore of the header and screw itinto the tissue. One of the wires in the electrically conducting coil 11is in its proximal end electrically connected to the first connector 7and in its distal end electrically connected to the helix 4, whereas theother wire in the electrically conducting coil is in its proximal endelectrically connected to the second connector 7′ and in its distal endelectrically connected to the ring electrode 5.

Reference is then made to FIGS. 5 and 6, in which are illustrated asecond embodiment of the flexible lead part 2 in a longitudinal sectionas well as a cross section through the lead, respectively. As in thefirst embodiment according to FIGS. 3 and 4, this embodiment has aninner tubular torque transferring member 9, formed in a similar way asin the first embodiment of five helical wires, and an inner fluid tighttubing 10. However, this embodiment has two separate electricallyconducting coils, one inner coil 17 and one outer coil 17′, separated byan intermediate fluid tight tubing 18. Each of the electricallyconducting coils is formed of one single wire 14 and 14′, respectively,having an electrically conducting core 15 and a surrounding electricallyinsulating layer 16, such that they form two coaxially arrangedinductance coils. Also this embodiment has an outer fluid tight tubing12.

As in the first embodiment, the tubular torque transferring member 9 isin its proximal end mechanically connected to the rotatable controlmember 8 and in its distal end mechanically connected to the helix 4,such that by rotating the control member it is possible to rotate thehelix and extend it out from the inner bore of the header and screw itinto the tissue. The inner electrically conducting coil 17 is in itsproximal end electrically connected to the first connector 7 and in itsdistal end electrically connected to the helix 4, whereas the outerelectrically conducting coil 17′ is in its proximal end electricallyconnected to the second connector 7′ and in its distal end electricallyconnected to the ring electrode 5.

Reference is then made to FIGS. 7 and 8 of the drawings, in which isillustrated an embodiment of a connection of the electrically conductingwires 14, 14′ to the electrodes as well as the tubular torquetransferring member 9 to the helix 4. FIGS. 7 and 8 are longitudinalsections through the distal portion of a medical implantable lead,according to the embodiment as illustrated and described in relation toFIGS. 3 and 4, with the helix being retracted and extended,respectively.

The longitudinal sections of FIGS. 7 and 8 are taken at the jointbetween the header 3, as seen to the right, and the distal end portionof the flexible lead part 2 as illustrated in FIGS. 3 and 4. The headeris made of a rigid material such as metal or a polymer and is formedwith an inner bore 19, in which the helix 4 is rotatably anddisplaceably accommodated. In the joint region between the header andthe flexible lead part, the electrically conducting ring electrode 5 isprovided, which also functions as a joint connector in that it comprisesa distal shoulder surface, in which the proximal end of the header 3 islocated and attached, and a proximal shoulder surface in which thedistal end of the flexible lead part 2 is located and attached. A shortdistance towards the distal end from the ring electrode 5, the lead isprovided with a fixed support member 20. Both the ring electrode 5 andthe support member 20 are formed with a through bore, through which ashaft 21 is rotatably and displaceably inserted, at the distal end ofwhich the helix 4 is mounted. The shaft 21 is of an electricallyconducting material and to prevent electrical connection between theshaft 21 and the ring electrode 5 as well as the support member 20, incase it is manufactured of an electrically conducting material,electrically insulating shaft bushings 22 are arranged in each of thethrough bores. To allow rotation and displacing of the helix 4 out fromand into the inner bore 19 of the header, the tubular torquetransmitting member is mechanically connected to the proximal end of theshaft. In case the tubular torque transferring member 9 is of anelectrically conducting material, the connection is arranged in anelectrically non-conducting fashion, such as via an electricallyinsulating sleeve 23 or the like. The electrically conducting coil ofthe lead comprises two electrically conducting wires 14, 14′, which areelectrically insulated from each other. To accomplish electricalconnection to each of the ring electrode 5 and the helix 4, one of theelectrical conducting wires 14′ is electrically connected to the ringelectrode 5, whereas the other electrically conducting wire 14 iselectrically connected to a sliding contact 24 arranged on the supportmember 20, the sliding contact being in permanent electrically contactwith the shaft 21, which is in electrically contact with the helix 4. Inthis way an electrically connection is ensured with the helix in spiteof the fact that the tubular torque transferring member 9 is notelectrically conducting and irrespective of the position of the helix.

The embodiment of FIGS. 7 and 8 are only an exemplifying embodiment ofhow the mechanical and electrical connections between the helix 4 andthe tubular torque transferring member 9 and the electrically conductingcoils 14, 14′, respectively, can be maintained as well as separated. Itis to be understood, however, that this embodiment is only exemplary andthat these functions can be realized also in many other different ways.

Now reference is made to FIGS. 9 to 11 for a detailed description of afirst embodiment of the arrangement of the connecting structure at theproximal end of the medical implantable lead according to the invention.As can be seen, the connecting structure is comprised of a thickenedportion 25 and a connector pin 26 protruding from the proximal end ofthe thickened portion. A first fluid tight sealing member 6 is arrangedaround the connector pin adjacent the proximal end of the thickenedportion. A second fluid tight sealing member 6′ is arranged around thethickened portion in an intermediate position of the same.

In prior art, normally the entire connector pin 26 is metallic andfunctions both as an electrical connector, which is in electricalconnection with an inner electrically conducting coil connected to thehelix at the distal end, as well as a rotatable control member forperforming rotation of the helix by being rotatably mounted in thethickened portion. However, according to the invention, the connectorpin is composed of an inner rotatable control member 8, which isconnected to the inner torque transferring member 9 and is rotatablyarranged within an outer, tubular electrically conducting connector 7,which in its turn is unrotatably mounted to the thickened portion andelectrically connected to the helix 4 at the distal end via anelectrically conducting coil 11, which is separated from the torquetransferring member 9.

In this embodiment, the torque transferring member 9 and the controlmember 8 are metallic and accordingly electrically conductive. Toprevent transfer of any electrical current, which may be induced intothe torque transferring member by a surrounding electromagnetic field,from the torque transferring member to the electrically conducting coil11 and hence to the helix 4, there is arranged an electricallyinsulating layer in form of an insulating tube 27 between the controlmember 8 and the connector 7. The insulating tube may optionally beunrotatably mounted to the connector 7, in which case the control member8 is rotatable inside the insulating tube, or be unrotatably mounted tothe control member, in which case the control member and the insulatingtube are jointly rotatable within the connector. In case the controlmember and/or the torque transferring member would be of an electricallynon-conductive material, the insulating tube could be dispensed with,since in that case no current can be induced into the torquetransferring member from an electromagnetic field.

The control member 8 is tubular with a through bore 28 to allowinsertion of a not shown guide wire through the control member and thetubular torque transferring member to the distal end of the lead. Thisis done for the purpose of performing guiding of the distal end of thelead, by means of the guide wire, to a desired position within a body,e.g. within a heart. As is evident from the drawings, in this embodimentthe control member 8 is located entirely within the connector 7. Toallow rotation of the control member, and hence also the torquetransferring member and the helix, the proximal end of the through bore28 in the control member is hexagonally formed to provide an engagementmeans 29 for a complementary formed rotary tool 30, as is illustrated inFIGS. 10 and 12. The rotary tool is formed with a body 31 and aprotruding shaft 32 having a hexagonal cross section to be inserted intothe hexagonally formed engagement means 29 in the control member 8. Alsothe rotary tool 30 is provided with a through bore 33 through the bodyand the shaft to allow insertion of the guide wire while the rotary toolis connected to the lead.

The thickened portion of the connecting structure comprises a proximalelectrically insulating portion 34, an intermediary electricallyconducting second connector 7′ and a distal electrically insulatingsleeve 35. The lead according to this embodiment is provided with onlyone electrically conducting coil 11. However, the electricallyconducting coil comprises two separate electrically conducting wires 14,14′, each surrounded by an electrically insulating layer 16, as isillustrated in FIGS. 3 and 4. One of the wires 14 is electricallyconnected to the helix 4 at the distal end and to the distal end of thefirst connector 7 within the proximal electrically insulated portion 34of the thickened portion of the connecting structure at the proximal endof the lead. The other electrically conducting wire 14′ of theelectrically conducting coil 11 is connected to the indifferentelectrode 5 at the distal end and to a distal end of the secondconnector 7′ which is formed as a protruding flange having a smallercross sectional dimension than the rest of the connector. Theconnections between the first and second electrically conducting wiresof the electrically conducting coil and the first and second connector,respectively, appears from FIGS. 9 and 10.

As is also seen from FIGS. 9 and 10, the outer fluid tight tubing 12 ofthe electrically conducting coil 11 is thread over the flange portion ofthe second connector 7′ and the outer flexible sleeve 35 is thread ontothe flange portion over the fluid tight tubing for protecting thetransition section between the connecting structure and the flexiblelead part.

Reference is then made to FIGS. 13-15 in which is illustrated a secondembodiment of the arrangement of the connecting structure at theproximal end of the medical implantable lead according to the invention.

As in the embodiment according to FIGS. 9-11, the connecting structureaccording to this embodiment comprises a thickened portion 25 and aconnector pin 26 protruding from the proximal end of the thickenedportion. A first fluid tight sealing member 6 is arranged around theconnector pin adjacent the proximal end of the thickened portion. Asecond fluid tight sealing member 6′ is arranged around the thickenedportion in an intermediate position of the same.

Moreover, the connector pin 26 is composed of an inner rotatable controlmember 8, which is connected to the inner torque transferring member 9and is rotatably arranged within an outer, tubular electricallyconducting connector 7, which in its turn is unrotatably mounted to thethickened portion and electrically connected to the helix 4 at thedistal end via an electrically conducting coil 11, which is separatedfrom the torque transferring member 9.

The torque transferring member 9 and the control member 8 are metallicand accordingly electrically conductive. To prevent transfer of anyelectrical current from the torque transferring member to theelectrically conducting coil 11 and hence to the helix 4, there isarranged an electrically insulating layer in form of an insulating tube27 between the control member 8 and the connector 7. The insulating tubemay optionally be unrotatably mounted to the connector 7, in which casethe control member 8 is rotatable inside the insulating tube, or beunrotatably mounted to the control member, in which case the controlmember and the insulating tube are jointly rotatable within theconnector.

The control member 8 is tubular with a through bore 28 to allowinsertion of a not shown guide wire through the control member and thetubular torque transferring member to the distal end of the lead. Thisis done for the purpose of performing guiding of the distal end of thelead, by means of the guide wire, to a desired position within a body,e.g. within a heart.

The thickened portion of the connecting structure comprises a proximalelectrically insulating portion 34, an intermediary electricallyconducting second connector 7′ and a distal electrically insulatingsleeve 35. The lead also according to this embodiment is provided withonly one electrically conducting coil 11, comprising two separateelectrically conducting wires 14, 14′, each surrounded by anelectrically insulating layer 16, as is illustrated in FIGS. 3 and 4.One of the wires 14 is electrically connected to the helix 4 at thedistal end and to the distal end of the first connector 7 within theproximal electrically insulated portion 34 of the thickened portion ofthe connecting structure at the proximal end of the lead. The otherelectrically conducting wire 14′ of the electrically conducting coil 11is connected to the indifferent electrode 5 at the distal end and to adistal end of the second connector 7′ which is formed as a protrudingflange having a smaller cross sectional dimension than the rest of theconnector. The connections between the first and second electricallyconducting wires of the electrically conducting coil and the first andsecond connector, respectively, appears from FIGS. 9 and 10.

As is also seen from FIGS. 9 and 10, the outer fluid tight tubing 12 ofthe electrically conducting coil 11 is thread over the flange portion ofthe second connector 7′ and the outer flexible sleeve 35 is thread ontothe flange portion over the fluid tight tubing for protecting thetransition section between the connecting structure and the flexiblelead part.

As described so far, this embodiment is identical with the firstembodiment. However, in this embodiment the connector pin 26 has asomewhat different structure. More precisely, the control member 8 isnot entirely surrounded by the connector 7. Instead the control memberprojects from the proximal end of the connector where it is formed withan increased proximal portion 36 having a cross sectional dimension thatis equal to the cross sectional dimension of the rest of the connectorpin and consequently the control member constitutes the outer surface ofthe proximal end of the connector pin. To insulate the control member 8electrically from the first connector 7, also the insulating tube 27between the control member and the connector is formed with an increasedproximal portion 37 having a cross sectional dimension that is equal tothe cross sectional dimension of the rest of the connector pin, suchthat the connector pin is provided with an insulating surface betweenthe control member and the first connector.

Moreover, the control member is not formed with any specific engagementmeans for engagement with a rotary tool, as in the embodiment accordingto FIGS. 9-11. To rotate the torque transferring member and the helixduring implanting of the lead inside a body, the proximal portion 36 mayinstead be gripped by means of an arbitrary gripping tool such as aclamp 38, as is illustrated in FIG. 16. The clamp 38 is made of anelastic material, such as a plastic, and comprises two shanks 39, 39′which are formed as one unitary piece and being connected in aconnecting portion 40 adjacent a lower end, wherein the clamp forms agripping portion 41 in form of a recess below the connecting portion.Accordingly, by gripping upper ends of the shanks 39, 39′ by hand, aphysician can displace them towards each other, in which case thegripping portion 41 in the lower end will open up due to elasticdeformation in the connecting portion 40 such that the gripping portionmay be positioned over the proximal portion 36 of the control member 8.Due to the elastic characteristics in the material, the gripping portionwill clamp around the control member such that the physician may rotatethe control member, and hence also the helix 4 at the distal end, byrotating the clamp 38.

Although modifications and changes may be suggested by those skilled inthe art, it is the intention of the inventors to embody within thepatent warranted heron all changes and modifications as reasonably andproperly come within the scope of their contribution to the art.

1.-10. (canceled)
 11. An MRI-compatible medical implantable leadcomprising: a lead body adapted to be implanted into a human or animalbody for monitoring and/or controlling an organ inside the body; aconnecting structure comprising a connector pin at a proximal end of thelead body, said connector pin comprising a rotatable control member; arotatable tubular torque transferring member connected to the rotatablecontrol member; a combined fixation means and electrode member in formof a helix at a distal end of the lead, said helix being connected tosaid rotatable tubular torque transferring member and being rotatable inrelation to the lead body and extendable out from said distal end, byrotation of the control member and the tubular torque transferringmember, for fixation of the lead to the organ; a connector at saidproximal end of the lead body electrically connected to the helix by atleast one electrically conducting wire formed as an electricallyconducting coil, said coil being separate from the tubular torquetransferring member and rotatably fixed in relation to the lead, wherebythe tubular torque transferring member is rotatably arranged within theelectrically conducting coil and having no electrically conductingfunction to or from the helix; said electrically conducting coilcomprising one or more individual wires, each comprising an electricallyconducting wire core and a surrounding electrically insulating layer;and said connector pin comprising said control member and saidconnector, said control member being rotatably arranged within saidconnector.
 12. A medical implantable lead according to claim 11, whereinthe control member is electrically insulated from the connector.
 13. Amedical implantable lead according to claim 11, wherein the controlmember and the connector are electrically insulated from each other byan electrically insulating member.
 14. A medical implantable leadaccording to claim 13, wherein the electrically insulating member is anelectrically insulating sleeve and the connector is arranged at theouter circumference of the insulating sleeve.
 15. A medical implantablelead according to claim 13, wherein the electrically insulating memberis in one unitary piece.
 16. A medical implantable lead according toclaim 13, wherein the electrically insulating member is non-rotatablymounted to said connector, and said control member is rotatable insidesaid insulating member.
 17. A medical implantable lead according toclaim 13, wherein the electrically insulating member is non-rotatablymounted to said control member, and said control member and saidelectrically insulating member are jointly rotatable within saidconnector.
 18. A medical implantable lead according to claim 11, whereinthat the connector is a metallic sleeve completely surrounding thecontrol member.
 19. A medical implantable lead according to claim 18,wherein the control member has a rotary engagement portion configured toengage a rotary tool.
 20. A medical implantable lead according to claim19, wherein the rotary engagement portion is a recess having engagementformations at the proximal end of the control member.
 21. A medicalimplantable lead according to claim 11, wherein the control memberprojects with a proximal portion beyond the connector at the proximalend of the lead body.
 22. A medical implantable lead according to claim21, wherein the proximal portion of the control member is adapted to begripped by a gripping tool for rotation of the control member.
 23. Amedical implantable lead according to claim 11, wherein said connectingstructure comprises a thickened portion and said connector isnon-rotatably mounted to said thickened portion.